Allowance for Loan Losses - Analysis of Past Due and Nonaccrual Loans (Detail) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due $ 10,172 $ 9,129
Current 1,978,573 1,603,620
Total orig. loans 1,988,745 1,612,749
> 90 Days and still accruing 0 0
Nonaccrual loans 22,824 32,529
PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 8,924 3,226
Current 485,064 613,652
Total orig. loans 493,988 616,878
> 90 Days and still accruing 0 0
Nonaccrual loans 5,398 1,646
Home Equity Lines of Credit [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 1,877  
Current 283,542  
Total orig. loans 285,419  
> 90 Days and still accruing 0  
Nonaccrual loans 3,379  
Home Equity Lines of Credit [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 367  
Current 28,968  
Total orig. loans 29,335  
> 90 Days and still accruing 0  
Nonaccrual loans 676  
Other Consumer [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 71  
Current 28,927  
Total orig. loans 28,998  
> 90 Days and still accruing 0  
Nonaccrual loans 21  
Other Consumer [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 23  
Current 3,344  
Total orig. loans 3,367  
> 90 Days and still accruing 0  
Nonaccrual loans 33  
C&I [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 2,221 899
Current 168,099 125,712
Total orig. loans 170,320 126,611
> 90 Days and still accruing 0 0
Nonaccrual loans 976 246
C&I [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 1 67
Current 19,743 40,832
Total orig. loans 19,744 40,899
> 90 Days and still accruing 0 0
30-59 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 4,635 5,519
30-59 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 7,259 2,668
30-59 Days [Member] | Home Equity Lines of Credit [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 1,033  
30-59 Days [Member] | Home Equity Lines of Credit [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 92  
30-59 Days [Member] | Other Consumer [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 12  
30-59 Days [Member] | C&I [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 2,197 739
30-59 Days [Member] | C&I [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 1 67
60-89 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 1,196 1,530
60-89 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 13 145
60-89 Days [Member] | Home Equity Lines of Credit [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 324  
60-89 Days [Member] | Other Consumer [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 40  
60-89 Days [Member] | Other Consumer [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 13  
60-89 Days [Member] | C&I [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   99
> 90 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 4,341 2,080
> 90 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 1,652 413
> 90 Days [Member] | Home Equity Lines of Credit [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 520  
> 90 Days [Member] | Home Equity Lines of Credit [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 275  
> 90 Days [Member] | Other Consumer [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 19  
> 90 Days [Member] | Other Consumer [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 10  
> 90 Days [Member] | C&I [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 24 61
Home Equity Loans [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 825 1,009
Current 33,892 22,550
Total orig. loans 34,717 23,559
> 90 Days and still accruing 0 0
Nonaccrual loans 1,195 1,197
Home Equity Loans [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 94 25
Current 3,924 6,960
Total orig. loans 4,018 6,985
> 90 Days and still accruing 0 0
Nonaccrual loans 109 25
Home Equity Loans [Member] | 30-59 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 402 615
Home Equity Loans [Member] | 30-59 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 23  
Home Equity Loans [Member] | 60-89 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 341 192
Home Equity Loans [Member] | > 90 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 82 202
Home Equity Loans [Member] | > 90 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 71 25
Auto Indirect [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   21
Current   91
Total orig. loans   112
> 90 Days and still accruing 0 0
Nonaccrual loans   18
Auto Indirect [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
> 90 Days and still accruing 0 0
Auto Indirect [Member] | 30-59 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   4
Auto Indirect [Member] | > 90 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   17
Construction [Member] | Residential [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Current   21,135
Total orig. loans 31,778 21,135
> 90 Days and still accruing 0 0
Nonaccrual loans 12 2,401
Construction [Member] | Residential [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Current 13,636 16,808
Total orig. loans 13,636 16,808
> 90 Days and still accruing 0 0
Construction [Member] | Commercial [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Current   24,545
Total orig. loans 66,285 24,545
> 90 Days and still accruing 0 0
Nonaccrual loans   99
Construction [Member] | Commercial [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 490  
Current 7,999 11,973
Total orig. loans 8,489 11,973
> 90 Days and still accruing 0 0
Nonaccrual loans 490  
Construction [Member] | > 90 Days [Member] | Commercial [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 490  
RE Mortgage [Member] | Residential [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 1,062 2,315
Current 206,523 152,279
Total orig. loans 207,585 154,594
> 90 Days and still accruing 0 0
Nonaccrual loans 3,045 3,430
RE Mortgage [Member] | Residential [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 3,164 2,304
Current 101,371 118,517
Total orig. loans 104,535 120,821
> 90 Days and still accruing 0 0
Nonaccrual loans 348 799
RE Mortgage [Member] | Commercial [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 4,116 1,635
Current 1,159,527 927,162
Total orig. loans 1,163,643 928,797
> 90 Days and still accruing 0 0
Nonaccrual loans 14,196 20,736
RE Mortgage [Member] | Commercial [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 4,785 260
Current 306,079 375,965
Total orig. loans 310,864 376,225
> 90 Days and still accruing 0 0
Nonaccrual loans 3,742 366
RE Mortgage [Member] | 30-59 Days [Member] | Residential [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 791 1,296
RE Mortgage [Member] | 30-59 Days [Member] | Residential [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 3,106 2,041
RE Mortgage [Member] | 30-59 Days [Member] | Commercial [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 200 735
RE Mortgage [Member] | 30-59 Days [Member] | Commercial [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 4,037 260
RE Mortgage [Member] | 60-89 Days [Member] | Residential [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   919
RE Mortgage [Member] | 60-89 Days [Member] | Residential [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   24
RE Mortgage [Member] | 60-89 Days [Member] | Commercial [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 491  
RE Mortgage [Member] | > 90 Days [Member] | Residential [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 271 100
RE Mortgage [Member] | > 90 Days [Member] | Residential [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 58 239
RE Mortgage [Member] | > 90 Days [Member] | Commercial [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due 3,425 900
RE Mortgage [Member] | > 90 Days [Member] | Commercial [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due $ 748  
Home Equity Lines of Credit [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   3,116
Current   302,050
Total orig. loans   305,166
> 90 Days and still accruing   0
Nonaccrual loans   4,336
Home Equity Lines of Credit [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   466
Current   37,931
Total orig. loans   38,397
> 90 Days and still accruing   0
Nonaccrual loans   346
Home Equity Lines of Credit [Member] | 30-59 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   2,066
Home Equity Lines of Credit [Member] | 30-59 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   275
Home Equity Lines of Credit [Member] | 60-89 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   296
Home Equity Lines of Credit [Member] | 60-89 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   118
Home Equity Lines of Credit [Member] | > 90 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   754
Home Equity Lines of Credit [Member] | > 90 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   73
Other Consumer [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   134
Current   28,096
Total orig. loans   28,230
> 90 Days and still accruing   0
Nonaccrual loans   66
Other Consumer [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   104
Current   4,666
Total orig. loans   4,770
> 90 Days and still accruing   0
Nonaccrual loans   110
Other Consumer [Member] | 30-59 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   64
Other Consumer [Member] | 30-59 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   25
Other Consumer [Member] | 60-89 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   24
Other Consumer [Member] | 60-89 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   3
Other Consumer [Member] | > 90 Days [Member] | Originated Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   46
Other Consumer [Member] | > 90 Days [Member] | PNCI Loans [Member]    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total past due   $ 76